FXUS63 KMQT 270918
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
418 AM EST FRI NOV 27 2009
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC SHOWING A LONGWAVE TROUGH OVER THE LOWER
GREAT LAKES AND MID ATLANTIC STATES...AND A BROAD RIDGE OVER THE
CANADIAN PRAIRIES AND CONUS NORTHERN PLAINS. A PRONOUNCED SHORTWAVE
IS COMING ASHORE OVER THE PACIFIC NORTHWEST. A SHORTWAVE IS SWEEPING
THROUGH EXTREME EASTERN U.P. INTO EASTERN ONTARIO. WEAKER SHORTWAVES
ARE OVER EASTERN MINNESOTA AND SOUTHERN MANITOBA. SURFACE ANALYSIS
DEPICTS A LOW OFF THE MID ATLANTIC STATES AND A RIDGE STRETCHING
NORTH ALONG THE MIDDLE AND NORTHERN MISSISSIPPI RIVER VALLEY. A
SURFACE THE LOW IS OVER SASKATCHEWAN WITH A WARM FRONT DRAPED SOUTH
THROUGH EASTERN DAKOTAS AND NEBRASKA.
&&
.DISCUSSION...
THE MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH TONIGHT. THE LONG
WAVE TROUGH AND ASSOCIATED LOW WILL TRACK TO NEW ENGLAND TODAY
ALLOWING THE RIDGE TO SHIFT OVER THE FORECAST AREA. WEAK SHORTWAVES
MOVING THROUGH THE RIDGE WILL SWEEP ACROSS THE FORECAST AREA.
MEANWHILE...THE CANADIAN SURFACE LOW WILL SETTLE SOUTH OVER THE
DAKOTA AND THE ACCOMPANYING FRONTAL SYSTEM WILL WEAKEN AS IT BECOMES
NEARLY STATIONARY OVER EASTERN DAKOTAS. WARM AIR ADVECTION WILL
INCREASE 850MB TEMPERATURE TO AROUND -3C OVER THE AREA GRADUALLY
REDUCING LAKE EFFECT ENHANCEMENT THROUGH THE DAY.
THE MID LEVEL RIDGE WILL SHIFT OVER THE FORECAST AREA WITH WEAK
SHORTWAVE ENERGY TONIGHT. THE SURFACE RIDGE WILL EXPAND OVER
THE AREA. WIND WILL BECOME LIGHT AND THE AIR MASS WILL BECOME FAIRLY
DRY. IN SPITE OF THE WEAK INSTABILITY ALOFT...THE DRY AIR AND STABLE
AIR IN THE LOW LEVELS WILL KEEP PRECIPITATION OUT. GFS FORECAST
SOUNDINGS SUGGEST THAT THERE WILL BE CONSIDERABLE CLOUD COVER
BETWEEN 850MB AND 700MB LIMIT RADIATIONAL COOLING THUS WILL KEEP
TEMPERATURES IN THE LOW TO MID 20S...WHICH WILL BE SLIGHTLY ABOVE
NORMAL FOR THIS TIME OF YEAR.
A WEAK SHORTWAVE WORKING ITS WAY THROUGH THE RIDGE WILL SWEEP ACROSS
THE FORECAST AREA ON SATURDAY. THE SURFACE LOW WILL LIFT OUT OF THE
PLAINS AND INTO SOUTHEAST IOWA. THE ACCOMPANYING FRONTAL SYSTEM WILL
SLIDE SOUTHEAST OF THE AREA AS WELL KEEPING ISENTROPIC ASCENT TO THE
SOUTH OF THE U.P. THIS WILL CONTINUE TO KEEP A STRONG NORTHERLY FLOW
OVER THE AREA. THE 850MB TEMPERATURE WILL REMAIN AROUND -2C OVER THE
AREA KEEPING LAKE EFFECT ENHANCEMENT TO A MINIMUM. CLOUD COVER WILL
REMAIN IN PLACE...LIMITING HEATING TO CAUSE TEMPERATURES TO CLIMB TO
ONLY AROUND 40. MEANWHILE...OUT WEST THE SHORTWAVE CONTINUES TO DIG
INTO A DEEPER TROUGH OVER THE SOUTHERN CALIFORNIA CAUSING A
SHORTWAVE TROUGH OVER THE NORTHERN PLAINS.
THE RIDGE LOOKS LIKE IT WILL FLATTEN OUT SATURDAY NIGHT AS A TROUGH
DIGS INTO THE NORTHERN PLAINS THEN INTO NORTHERN MINNESOTA. ENERGY
WILL ROTATE AROUND THE BASE OF THE TROUGH WHICH WILL SLIDE ACROSS
THE CWA BEGINNING SATURDAY NIGHT. THE SURFACE LOW WILL MOVE TO
SOUTHERN U.P. DRAGGING THE COLD FRONT THROUGH THE MISSISSIPPI RIVER
VALLEY AND WISCONSIN. THE AIR MASS WILL CONTINUE TO BE FAIRLY DRY.
THE 850MB TEMPERATURES WILL CHILL TO -5C SUPPORTING SOME POSSIBLE
LAKE EFFECT ENHANCEMENT. THEREFORE...I PLAN TO GO WITH ONLY A
SLIGHT CHANCE AT THIS TIME.
THE MID LEVEL TROUGH MOVING THROUGH MINNESOTA WILL FINALLY SWEEP
ACROSS THE FORECAST AREA ON SUNDAY. STRONG 850-500MB Q-VECTOR
CONVERGENCE ACROSS THE U.P. WHILE THE ISENTROPIC ANALYSIS SHOWING
MAINLY SUBSIDENCE. THE AIR MASS MOVING THE AREA WILL BE NEARLY
SATURATED...SO WILL BUMP UP POPS.
WEAK SHORTWAVES WILL FOLLOW DURING SUNDAY NIGHT AS THE MAIN IMPULSE
OF THE LONGWAVE SHIFT INTO EASTERN ONTARIO. WEAK ISENTROPIC ASCENT
WILL ALSO BE POSSIBLE OVERNIGHT. HOWEVER THE BIGGEST IMPACT WILL
COME FROM THE DELTA-T OVER LAKE SUPERIOR AS THE 850MB TEMPERATURES
COOLS TO -10C. THUS WILL BE LOOKING FOR LAKE EFFECTS MAINLY OVER THE
NORTHERN SECTORS.
ANOTHER SHORTWAVE RIDING DOWN THE LEE OF THE APPROACHING RIDGE AND
THE 280K ISENTROPIC ASCENT AHEAD OF THE SURFACE LOW SLIDING OUT OF
CENTRAL CANADA WILL COMBINE TO BRING MORE PRECIPITATION TO THE AREA.
THE 850MB TEMPERATURES WILL GRADUALLY WARM BUT NOT ENOUGH TO DROP
THE SNOW WORDING FOR MONDAY. THE ECMWF APPEARS TO REMAIN COOL ENOUGH
ALOFT TO KEEP THE PRECIPITATION AS SNOW FOR MONDAY NIGHT...
WHEREAS...GFS WARMS IT A BIT FAVORING MORE OF A MIX OF RAIN AND
SNOW. I WILL LEAVE THE GRIDS ALONE FOR NOW UNTIL NEW GRIDS COME IN.
&&
.AVIATION /FOR THE 06Z TAF ISSUANCE/...
MVFR CONDITIONS WILL CONTINUE THROUGH THE AFTERNOON AT BOTH SITES
WITH LAKE EFFECT CLOUDS CONTINUING TO MOVE THROUGH THE AREA. DRIER
AIR AND LIGHT WINDS BY EVENING WILL IMPROVE CONDITIONS TO VFR AT
BOTH SITES.
&&
.MARINE /FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE/...
NORTHERLY WINDS TO 30 KNOTS OVER EASTERN LAKE SUPERIOR WILL DIMINISH
BELOW 20 KNOTS THIS AFTERNOON. EXPECT LIGHT WINDS THEREAFTER AS A
HIGH PRESSURE RIDGE REMAINS OVER LAKE SUPERIOR THROUGH SATURDAY
NIGHT. ON SUNDAY WEAK LOW PRESSURE WILL MOVE ACROSS LOWER MICHIGAN
FROM THE SOUTHWEST...ALLOWING WINDS TO INCREASE TO 20 TO 25 KNOTS
OUT OF THE NORTHWEST THROUGH SUNDAY BEFORE BACKING WEST ON MONDAY.
ON TUESDAY WINDS WILL BACK SOUTHWEST AHEAD OF A CLIPPER SYSTEM THAT
WILL CROSS THE UPPER GREAT LAKES TUESDAY NIGHT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
DISCUSSION...DLG
AVIATION...07
MARINE...PEARSON
